Lock nut having a conically tapered reduced end portion



y 1959 A. M. PASINSKIY 2,886,087

LOCK NUT HAVING A CONICALLY TAPERED REDUCED END PORTION Filed July 11,1956 mmvmx ARTHUR M. PAS/NSKI By M ATTORNEY United States Patent LOCKNUT HAVING A CUNlCALLY TAPERED RElDUtIED END PORTIQN Arthur M.Pasinslri, Detroit, Mich, assignor to Burroughs Corporation, Detroit,Mich, a corporation of Michigan Application July 11, 1956, Serial No.597,217

1 Claim. (Cl. 151-49) This invention relates to an improved lock nutconstruction for use with a threaded member such as a bolt and the like.

The invention has for its objects to provide a reuseable lock nut whichis of unitary, one piece construction that is simple and inexpensive tomanufacture, which is of minimum axial length or thickness, and whichprovides positive reliable locking action without requiring a largeapplication of torque for tightening the nut.

In accordance with the present invention, there is provided aninternally threaded lock nut having an integrally formed, reducedshoulder section in the form of a tapered axial hub or nipple projectingfrom one face thereof a distance slightly less than the pitch of thethread in the nut. The diameter of the nipple or shoulder adjacent thebody of the nut is slightly greater than the major diameter of thethread. The tapered end of the nipple is reduced to a dimension which,measured from the axis of the, bore in the nut, is slightly less thanthe major radial dimension of the thread and severs a portion of thethread beyond the face of the nut, thereby interrupting the peripheralcontinuity of the conical nipple. Thus when the nut is applied to athreaded member such as a bolt that passes through a cylindrical openingin one or more interposed mechanical parts, a portion of theperipherally discontinuous, tapered nipple is received within and seatsagainst the wall of the opening in the adjacent part, and is caused tobe elastically deformed and wedged tightly against the wall of theopening and the threads of the bolts as the nut is drawn up on the bolt.

The nature of the present invention together with the above and otherobjects, features, and advantages thereof will appear more fully fromthe following detailed description and drawings: wherein Fig. l is aside elevation View of a lock nut formed in accordance with the presentinvention;

Fig. 2 is a perspective view of the lock nut of Fig. 1;

Figs. 3 and 4 are side elevation views of the nut applied to a bolt forfastening a pair of interposed members and illustrate the nut in itsretracted and in its tightened or locked position, respectively, on thebolt;

Fig. 5 illustrates the invention in a jam nut application in which apair of lock nuts on a threaded member are used to lock an interposedpart in any desired angular position; and

Fig. 5A is a view taken in the direction A-A of Fig. 5.

Referring to the drawings, Fig. 1 illustrates a hexagonal lock nut inaccordance with the invention having an integrally formed, reducedcentral section in the form of tapered axial nipple or shoulder 12projecting from one face 14 thereof. The nut is shown threadedthroughout its length, including the length of the reduced section, witha standard 45 degree V-thread, the major diameter of which is indicatedby the dimension B and the minor diameter by A.

In accordance with the invention, the axial length C of the reducedsection measured from the body of the nut to the forwardmost edgethereof is slightly less than the distance between a pair of threads inthe nut or the pitch 2 of the thread. The diameter L of the hub orstem-like reduced shoulder section joining the body or face of the nutis slightly greater than the major diameter B of the thread, while thetapered end of the shoulder is reduced to a dimension slightly less thanthe major diameter of the thread in the nut. The reduction at thetapered end of the shoulder should be sufiicient to cause the forwardedge of the shoulder to intersect and sever a portion of the threadbeyond the face of the nut. The conical surface of the axial shoulder,therefore, will have a segment removed therefrom corresponding to thehelical excursion of the thread in the nut, and its forward edge willvary radially between the major and minor diameters of the thread anddefine a helix coinciding with the helical convolution of the thread inthe portion of the shoulder attached to the nut.

The peripheral discontinuity and helicalformation of the forward edge oftapered shoulder 12 are best seen in Fig. 2. The helix emerges from apoint on the face of the nut and terminates approximately one turntherefrom at a point which is axially displaced from the face of the nuta distance slightly less than the turn of one thread and is spacedradially from the axis of the nut a distance slightly less than theradius of the major diameter of the thread.

The nut is illustrated in Figs. 3 and 4 applied to a threaded membersuch as a headed bolt it) for fastening a pair of mechanical parts 22,24, such as a pair of panel members, for example, having alignedcylnidrical openin-gs 26, 28 therein for receiving the shank of thebolt. The relative diameter of the panel openings to the diameter of thebolt will be dictated by individual engineering standards, but, forpurposes of illustration and not to be taken in a limiting sense, thediameter of the panel opening may be greater than the major diameter ofthe threaded bolt and nut members by, say, approximately 6.001 inch. Thediameter of the tapered shoulder at its base or enlarged end adjacentthe body of the nut may be, say, 000510.0005 inch greater than the majordiameter of the thread.

Since the tapered end of the shoulder is slightly smaller than theopening at the face of the panel member and the enlarged end is greaterthan the diameter of the opening, the forward end of the shoulder willfreely enter the opening up to a point where the outer radial dimensionof the shoulder is equal to the radius of the opening, causing anintermediate portion of the shoulder to seat against the forward edge ofthe wall of the openmg.

The nut is composed preferably of comparatively hard, non-ductilematerial which is at least as hard as the material of the part or partsfastened thereby, so that the material of the shoulder will not expandor flow into the opening as the nut is drawn up on the threaded memberagainst the panel. Owing also to the peripheral discontinuity of theshoulder, its resistance to radial contraction or deflection isconsiderably weakened, and its forward edge will be elastically orresiliently deformed under the application of force thereto. Thus, asthe nut is tightened on the bolt, it will wedge or cam against the wallof the opening and its resilient forward edge will bend slightly andfirmly grip and engage the thread of the nut, frictionally locking thenut thereto.

Since the surface of the reduced section is not of con tinuoustransverse formation, the force or torque applied to tighten the nut isnot distributed uniformly around the surface of the shoulder. Therefore,a lesser amount of pressure will be required to tighten and lock the nutthan otherwise would be required if its surface were continuous in aplane transverse to the axis of the shoulder and there assaos'? werecontinuous line contact of the nipple with the wall of the opening inthe plane of the opening.

By reason of the present construction, no destruction or permanentdeformation of the shoulder is encountered.

The original shape and dimensions of the shoulder are restored when thenut is backed-off and disassembled from the bolt, thereby enabling thenut to be salvaged and to be used again for other applications.

In the jam nut application illustrated in Figs. and 5A, severalapertured mechanical elements 30, 32 and 34 are shown located axially ofand locked to a threaded member such as a worm shaft 36 by separatepairs of lock nuts 38, 40; 42, 44 and 46, 48. The relative dimensions ofthe openings in the parts to the tapered end and to the enlarged end ofthe reduced shoulder of each nut may be the same as specifiedhereinabove. The parts 30, 32 and 34 may be cam elements, one of whichis illustrated in Fig. 5A, such as are employed in rotary timingswitches in which the cams are located on a shaft in predeterminedangular positions relative to a reference axial plane. Conventional locknuts have been found to loosen under the shock and vibration conditionsencountered in applications of this character, thereby losing thecritical angular position of the cam and causing malfunction of thetiming switches and apparatus associated therewith. The lock nuts of thepresent invention, however, have been found to provide positive reliablelocking action after continued prolonged operations.

Since the axial length of the nipple is slightly less than the distanceof one thread from the face of the nut and a substantial portion of thenipple is received within the opening in the member 22, the distance sfrom the memher to the face of nut can be held to a minimum. Thisdistance will be less than the corresponding distance to the face of thenut presented with other locking devices that require a separate,additional locking member, such as a washer, interposed between themember 22 and the face of the nut. The overall axial length or thicknessof the one piece lock nut of the present invention, therefore, can bemade less than that of such other multiple part locking devices of theabove character, thereby permitting the instant lock nut to be employedwhere minimum axial clearance is available.

The nut is well adapted to fabrication by automatic screw machineprocesses but can be formed by various other mechanical processes aswell as by molding or casting. Where the nut is formed by machining orgrinding, the tapered axial shoulder may be formed by undercutting atransverse section of the nut or stock the axial thickness of which isno greater than the pitch of one thread of the nut, reducing the sectionto a dimension that is slightly greater than the radial dimension of theinner or major diameter of the threaded nut as measured from the axis ofthe nut, and simultaneously or subsequently tapering the reduced sectionuntil the end of the shoulder opposite the face of the nut justintersects or is very slightly less than the major radial dimension ofthe threaded nut.

For most cases that will be encountered, the difference between thedimension L of the enlarged end of the shoulder and the major diameter Bof the thread will be no greater than and will usually be less than thedifference BA between the major and minor diameters of the thread. Theangle that the tapered shoulder makes with the face of the nut then maybe taken approximately as the supplement of the angle whose tangent isequal to the quotient of the pitch p of the thread divided by onehalfthe difference of BA or Preferably the nut or rod stock from which thenut is formed is bored and threaded prior to reducing an end section ofthe nut to form the tapered axial shoulder. If desired, however, thetapered shoulder can be formed prior to the tapping operation. In thisevent, the axial length of the shoulder may be made equal to the pitchof the proposed thread. Then, by making the diameter of the enlarged endof the shoulder slightly greater than the major diameter of the threadand the diameter of its tapered end less than the major diameter of thethread, upon the subsequent tapping of the nut, the major diameter ofthe tap will intersect and sever a portion of the surface of theshoulder and impart thereto the peripheral discontinuity describedherein.

The above described embodiments illustrate but a few of the manypossible applications of the present invention. It is apparent that theprinciples of the invention may be applied to lock nuts having shapesand thread formations other than those illustrated herein.

I claim:

A combined lock and fastening nut of unitary, onepiece constructioncomprising a body portion having a plurality of threads therein and anintegrally formed, right comically tapered nipple section presenting ahelically-extending, forwardly-facing portion that projects axially froma face of the body portionof the nut, and forms a continuation of a truethread face extending through the nut, said nipple portion merging intothe face of the nut body at a point displaced slightly less than onefull turn of the helical convolution of the outer edge of the nipplesection from its most forward terminal point, the diameter of the nippleend portion displaced from the nut body gradually increasing from aminimum dimen sion that is less than the major diameter of a thread inthe nut to a maximum dimension greater than the major diameter of thethread, the aforesaid point where the outer edge of the nipple sectionmerges into the face of the nut body corresponding to the point wherethe nut thread emerges from the face of the body portion of the nut.

References Cited in the file of this patent UNITED STATES PATENTS901,810 Hemsteger Oct.20, 1908 1,928,769 Teetor Oct. 3, 1933 2,278,962Young Apr. 7, 1942 2,288,959 Squire July 7, 1942 2,542,023 Friedman Feb.20, 1951 FOREIGN PATENTS 691,000 France July 1, 1930

